In horizontal drilling technology, the obstacles in front of the drill head of the drilling device represent a problem. These types of obstacles may be, for example, hard rock fragments that often cannot be demolished by the drilling devices being used. Furthermore, there may also be water lines, gas lines, telephone lines, and/or electrical lines in the ground close to the surface that must not be destroyed by drilling.
This problem has led to the development of controlled horizontal drilling devices. With these types of drilling devices, characterized as HDD, it is possible to bypass obstacles. The process of obstacle locating via geo-radar exploration is known in order to bypass the obstacles due to the locating.
Normally, the drill head of a horizontal drilling device is the most greatly loaded component, because it is used to transfer the static and dynamic (if there is a percussive device) drilling forces, generated by a drive unit on the horizontal drilling device, to the ground. The drill head is attached on the foremost end of a drill pipe, in which the drill pipe usually consists of a plurality of linkages, connected to one another, for example, via screw closures. The rear end of the drill pipe may be connected to a drive unit, by means of which forces may be transferred to it in the longitudinal direction of the drill pipe, as well as a torque. The drill pipe, including the drill head attached to it, may be driven in the direction of thrust and retraction, as well as rotationally, by means of the drive unit.
The drill head may be a so-called controlled drill head whose front surface, at least in certain areas, is tilted with respect to its own longitudinal axis and, consequently, with respect to the drilling device.
When ground drilling with drilling fluid (flushing fluid), one problem that occurs is so-called “blowouts.” If the drilling channel has collapsed, for example, or if there is not sufficient backflow of a drilling fluid being used, along the drilling channel, for other reasons, the pressure in the drilling channel will increase. If this pressure increase in the drilling channel is not detected, this can lead to an uncontrolled blowout of drilling fluid at the surface, which can lead to environmental contamination. There can also be rises or depressions in the ground which means that, for example, roads and parts of buildings may rise up or sink. Therefore, it is desirable to measure the pressure in the drilling channel.